biostudies-literatureUnknown5(3)Song HNational Natural Science Foundation of ChinaExtinction selectivity determines the direction of macroevolution, especially during mass extinction; however, its driving mechanisms remain poorly understood. By investigating the physiological selectivity of marine animals during the Permian-Triassic mass extinction, we found that marine clades with lower O<sub>2</sub>-carrying capacity hemerythrin proteins and those relying on O<sub>2</sub> diffusion experienced significantly greater extinction intensity and body-size reduction than those with higher O<sub>2</sub>-carrying capacity hemoglobin or hemocyanin proteins. Our findings suggest that animals with high O<sub>2</sub>-carrying capacity obtained the necessary O<sub>2</sub> even under hypoxia and compensated for the increased energy requirements caused by ocean acidification, which enabled their survival during the Permian-Triassic mass extinction. Thus, high O<sub>2</sub>-carrying capacity may have been crucial for the transition from the Paleozoic to the Modern Evolutionary Fauna.Innovation (Cambridge (Mass.))100618https://www.ebi.ac.uk/biostudies/studies/S-EPMC11025005biostudies-literatureRespiratory protein-driven selectivity during the Permian-Triassic mass extinction.PMC11025005Tian LDal Corso JChu DFeng YFoster WJWang FSong HWu YDai XfalseRespiratory protein-driven selectivity during the Permian-Triassic mass extinction.Extinction selectivity determines the direction of macroevolution, especially during mass extinction; however, its driving mechanisms remain poorly understood. By investigating the physiological selectivity of marine animals during the Permian-Triassic mass extinction, we found that marine clades with lower O<sub>2</sub>-carrying capacity hemerythrin proteins and those relying on O<sub>2</sub> diffusion experienced significantly greater extinction intensity and body-size reduction than those with higher O<sub>2</sub>-carrying capacity hemoglobin or hemocyanin proteins. Our findings suggest that animals with high O<sub>2</sub>-carrying capacity obtained the necessary O<sub>2</sub> even under hypoxia and compensated for the increased energy requirements caused by ocean acidification, which enabled their survival during the Permian-Triassic mass extinction. Thus, high O<sub>2</sub>-carrying capacity may have been crucial for the transition from the Paleozoic to the Modern Evolutionary Fauna.2024-01-01T00:00:00Z2024 May2026-06-01T10:48:47.946Z2026-04-08T11:37:57.369ZS-EPMC110250053863858310.1016/j.xinn.2024.100618